1. Field of the Invention
The present invention relates to ink-jet recording heads and ink-jet recording apparatuses using the same. In particular, the present invention relates to an ink-jet recording head, a circuit board for an ink-jet recording head, an ink-jet recording head cartridge, and an ink-jet recording apparatus in which bubbles are produced in ink by using thermal energy generated by heat-generating resistors and the ink for recording is ejected by expansion and contraction of the bubbles and in which the resistance of wiring electrodes for supplying electric power to the heat-generating resistors is made uniform between each wiring electrode.
2. Description of the Related Art
Various ink-jet recording heads are known, in which ink droplets to be ejected are formed in different ways. Conventional recording apparatuses use these recording heads which perform recording in such a manner that the ejected ink droplets adhere to recording media such as sheets of paper. In particular, the ink-jet recording heads which use heat as an energy for producing the ink droplets to be ejected can be provided relatively easily with multiple ink ejection ports disposed in high density, whereby high speed, high resolution, and high quality recording is made possible.
A so-called side-shooter-type ink-jet recording head is known as a recording head which ejects ink by using thermal energy. In the side-shooter-type ink-jet recording head, ink droplets are upwardly ejected substantially in perpendicular to a plane along which heat-generating resistors for generating thermal energy are disposed. In the recording head of this type, the ink is generally supplied through an ink supply opening which is formed passing through a circuit board provided with the heat-generating resistors, the ink being supplied from the rear side of the circuit board.
FIGS. 22 and 23 show the known side-shooter-type inkjet recording head. FIG. 22 is a perspective view of a part of the circuit board, which is exposed by cutting away a part of a member which defines ink ejection ports. FIG. 23 mainly shows wiring electrodes in plan provided on the circuit board of the recording head.
In the side-shooter-type ink-jet recording head shown in FIG. 22, a plurality of electrothermal transducers (hereinafter referred to as heaters) 802 disposed on a circuit board 805 and in a staggered way at sides of an ink supply opening 803 which is formed passing through the circuit board 805. The circuit board 805 is provided with a member formed thereon, which defines ink ejection ports 801 opposing the respective electrothermal transducers 802 and associating with ink flow paths 804.
The circuit board 805 shown in FIG. 23 is provided thereon with source-side common wiring electrodes 902a and 902b for selectively driving the plurality of heaters 802 to eject ink in accordance with recording data, heat-generating resistors forming the electrothermal transducers 802 and wiring electrodes for supplying electric power thereto, driving devices such as transistors (shown in black in the drawing and formed at a lower layer side), and ground-side common wiring electrodes 904a and 904b. These wiring electrodes and circuits are connected in series to each other. Each source-side or ground-side common wiring electrode 902a or 902b, or 904a or 904b can be electrically connected to the outside of the circuit board 805 through electrode pads 903. Inter-layer insulative films, protective films, and the like are omitted from these drawings.
In the ink-jet recording head thus formed, ink is held so as to form a meniscus in the vicinity of each ink ejection port 801. The ink is quickly boiled at heated surfaces by using thermal energy produced by the heaters 802 selectively driven in accordance with recording data, whereby the ink is ejected by pressure of bubbles generated when the ink is boiled.
Electric energy or power to be applied to a heater for ejecting ink is an important factor which affects the quality of ink ejection. That is, when the electric energy varies, the state of ink-bubble development varies, whereby there is a risk that the ink is not ejected as designed. For example, when the electric energy, that is, driving energy is not sufficiently applied, there is a risk that film boiling of the ink is unstably performed, whereby the speed, direction, and amount of ejection of the ink droplets may vary, thereby deteriorating the quality of recorded images and producing kinks, shabbiness, scratchiness, etc. When the driving energy is excessively applied, a mechanical stress is given to the electrothermal transducers and film boiling of the ink is unstably performed, whereby the quality of ejection of the ink droplets is deteriorated, as described above, and the recording head may be damaged in the worst case.
Therefore, energy having the same value is preferably inputted into each of the plurality of heaters and the amount of the energy to be inputted into each heater is preferably constant.
It is known that the amount of energy inputted to each heater varies when the number of heaters of a head driven at the same time varies. That is, the voltage-drop value varies according to the number of heaters driven at the same time which varies according to the recording data and the like, thereby changing the driving energy inputted to each heater.
A configuration as a countermeasure to this problem is devised in that, as shown in FIG. 23, wiring electrodes between the heaters 802 and the electrode pads 903 and between the driving devices and the electrode pads 903 are divided into a plurality of wiring electrodes, and a resistance value in each wiring electrode 902a, 902b, 904a, or 904b is substantially the same, for example, as disclosed in Japanese Patent Laid-Open No. 10-44416. With this arrangement, the difference in voltage drop at each common wiring electrode between a case in which all the heaters are driven and the case in which a single heater is driven can be reduced, whereby the same amount of driving energy can be applied to each heater.
In the above known configuration, the voltage drop produced when driving the heaters due to the common wiring electrodes is reduced. The resistance of wiring is reduced by increasing the width of each common wiring electrode 902a, 902b, 904a, or 904b, and the resistance of the wiring electrodes 902a, 902b, 904a, and 904b is made uniform by differing the widths of the common wiring electrodes 902a, 902b, 904a, and 904b from each other according to the lengths of the common wiring electrodes 902a, 902b, 904a, and 904b, respectively, as widths A and B shown in FIG. 23 differ from each other.
Recently, ink-jet recording apparatuses generally use recording heads each provided with a plurality of heaters highly densely integrated with each other so as to obtain high-resolution and high-quality images at high speeds. On the other hand, the recording heads are required to be reduced in size. Therefore, it is very difficult to uniform resistance values of wiring electrodes from electrode pads to heaters only by controlling the width of each wiring electrode under the condition in which the size of the recording head cannot be increased.
Since the size of a circuit board is increased when intending to uniform the resistance of wiring electrodes only by controlling the width of each wiring electrode, manufacturing costs are increased because the number of substrates obtained from one silicon wafer is reduced, and the size of the recording head is increased due to the increased size of the substrate. When a plurality of heaters are driven according to divided time-sharing groups, variations in the amount of driving energy to be applied may be reduced by increasing the number of divisions in timesharing groups, thereby reducing the number of heaters which are simultaneously driven. However, the recording head is generally driven at a high frequency due to the requirement for high-speed recording, and driven periods are made shorter when increasing the number of divisions in timesharing groups. Therefore, it is difficult to further reduce the width of a driving pulse by increasing the number of divisions in time-sharing groups in consideration of the responsiveness of the driving devices. Although the reduction corresponding to the voltage drop of the applied driving energy may be compensated for by pulse-width modulation, it is necessary to have a logical circuit for controlling the driving energy to be constant, and the manufacturing costs may thereby increase.
Accordingly, it is an object of the present invention to provide an ink-jet recording head, a circuit board for an ink-jet recording head, an ink-jet recording head cartridge, and an ink-jet recording apparatus in which the resistance of wiring electrodes are made substantially the same between each wiring electrode without increasing the size of the ink-jet recording head.
To the end, according to a first aspect of the present invention, a circuit board for an ink-jet recording head which ejects ink comprises a plurality of electrothermal transducers for generating thermal energy which is used for ejecting ink; and a plurality of wiring electrodes for supplying electric power to the plurality of electrothermal transducers, the plurality of wiring electrodes each having a thickness of one of at least two values.
According to a second aspect of the present invention, a circuit board for an ink-jet recording head which ejects ink comprises a plurality of electrothermal transducers for generating thermal energy which is used for ejecting ink; and a plurality of wiring electrodes for supplying electric power to the plurality of electrothermal transducers, the plurality of wiring electrodes each having a plurality of layers which are successively formed by using wiring-electrode-forming patterns. The thickness of each of the plurality of wiring electrodes differs from that of the other wiring electrodes by differing each of the wiring-electrode-forming patterns from the others.
According to a third aspect of the present invention, a circuit board for an ink-jet recording head which ejects ink comprises a plurality of electrothermal transducers for generating thermal energy which is used for ejecting ink; and a wiring unit for applying electric power supplied from the outside to the plurality of electrothermal transducers, the wiring unit being divided into a plurality of wires each formed with a plurality of layers and provided with an electrode pad for receiving the electric power. The resistance of the plurality of wires between the electrode pads and the electrothermal transducers is substantially the same for each wire.
According to a fourth aspect of the present invention, an ink-jet recording head for ejecting ink comprises a circuit board which comprises a plurality of electrothermal transducers for generating thermal energy which is used for ejecting ink; and a plurality of wiring electrodes for supplying electric power to the plurality of electrothermal transducers, the plurality of wiring electrodes each having a thickness of one of at least two values.
According to fifth aspect of the present invention, an ink-jet recording head for ejecting ink comprises a circuit board which comprises a plurality of electrothermal transducers for generating thermal energy which is used for ejecting ink; and a plurality of wiring electrodes for supplying electric power to the plurality of electrothermal transducers, the plurality of wiring electrodes each having a plurality of layers which are successively formed by using wiring-electrode-forming patterns. The thickness of each of the plurality of wiring electrodes differs from that of the other wiring electrodes by differing each of the wiring-electrode-forming patterns from the others.
According to a sixth aspect of the present invention, an ink-jet recording head for ejecting ink comprises a circuit board which comprises a plurality of electrothermal transducers for generating thermal energy which is used for ejecting ink; and a wiring unit for applying electric power supplied from the outside to the plurality of electrothermal transducers, the wiring unit being divided into a plurality of wires each formed with a plurality of layers and provided with an electrode pad for receiving the electric power. The resistance of the plurality of wires between the electrode pads and the electrothermal transducers is substantially the same for each wire.
According to seventh aspect of the present invention, an ink-jet recording head cartridge comprises an ink-jet recording head for ejecting ink, which comprises a circuit board, and an ink tank for receiving ink to be supplied to the ink-jet recording head. The circuit board comprises a plurality of electrothermal transducers for generating thermal energy which is used for ejecting ink; and a plurality of wiring electrodes for supplying electric power to the plurality of electrothermal transducers, the plurality of wiring electrodes each having a thickness of one of at least two values.
According to an eighth aspect of the present invention, an ink-jet recording head cartridge comprises an ink-jet recording head for ejecting ink, which comprises a circuit board, and an ink tank for receiving ink to be supplied to the ink-jet recording head. The circuit board comprises a plurality of electrothermal transducers for generating thermal energy which is used for ejecting ink; and a plurality of wiring electrodes for supplying electric power to the plurality of electrothermal transducers, the plurality of wiring electrodes each having a plurality of layers which are successively formed by using wiring-electrode-forming patterns. The thickness of each of the plurality of wiring electrodes differs from that of the other wiring electrodes by differing each of the wiring-electrode-forming patterns from the others.
According to a ninth aspect of the present invention, an ink-jet recording head cartridge comprises an ink-jet recording head for ejecting ink, which comprises a circuit board, and an ink tank for receiving ink to be supplied to the ink-jet recording head. The circuit board comprises a plurality of electrothermal transducers for generating thermal energy which is used for ejecting ink; and a wiring unit for applying electric power supplied from the outside to the plurality of electrothermal transducers, the wiring unit being divided into a plurality of wires each formed with a plurality of layers and provided with an electrode pad for receiving the electric power. The resistance of the plurality of wires between the electrode pads and the electrothermal transducers is substantially the same for each wire.
According to a tenth aspect of the present invention, an ink-jet recording apparatus comprises an ink-jet recording head for ejecting ink which comprises a circuit board. The circuit board comprises a plurality of electrothermal transducers for generating thermal energy which is used for ejecting ink; and a plurality of wiring electrodes for supplying electric power to the plurality of electrothermal transducers, the plurality of wiring electrodes each having a thickness of one of at least two values.
According to an eleventh aspect of the present invention, an ink-jet recording apparatus comprises an inkjet recording head for ejecting ink which comprises a circuit board. The circuit board comprises a plurality of electrothermal transducers for generating thermal energy which is used for ejecting ink; and a plurality of wiring electrodes for supplying electric power to the plurality of electrothermal transducers, the plurality of wiring electrodes each having a plurality of layers which are successively formed by using wiring-electrode-forming patterns. The thickness of each of the plurality of wiring electrodes differs from that of the other wiring electrodes by differing each of the wiring-electrode-forming patterns from the others.
According to a twelfth aspect of the present invention, an ink-jet recording apparatus comprises an ink-jet recording head for ejecting ink which comprises a circuit board. The circuit board comprises a plurality of electrothermal transducers for generating thermal energy which is used for ejecting ink; and a wiring unit for applying electric power supplied from the outside to the plurality of electrothermal transducers, the wiring unit being divided into a plurality of wires each formed with a plurality of layers and provided with an electrode pad for receiving the electric power. The resistance of the plurality of wires between the electrode pads and the electrothermal transducers is substantially the same for each wire.
Since at least one of the plurality of wiring electrodes, according to the present invention, has a thickness of one of at least two values, the resistance of the plurality of wiring electrodes can be controlled so as to be the same for each wiring electrode by differing the thickness of each wiring electrode from that of the other wiring electrodes. With this arrangement, the area of a circuit board for wiring electrodes can be reduced compared with a case in which the resistance of wiring electrodes is controlled only by varying the width of each wiring electrode.
According to the present invention, an ink-jet recording head is obtainable without increasing the size of a circuit board of the ink-jet recording head, in which the resistance of wiring electrodes provided on the circuit board is uniform and the variations in driving energy inputted to each heater are thereby reduced.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.